The present invention relates to an ignition system, for use in an internal combustion engine having a cylinder housing with an air or water cooled region, for achieving multiple ignition by means of at least a pair of spark plugs connected electrically in series and including a first spark plug mounted in the cylinder housing while being electrically isolated therefrom and the second spark plug mounted directly, for example by threading, into a cylinder head of the cylinder housing. The present invention further relates to an assembly of components of an internal combustion engine including a cylinder housing thereof in combination with such an ignition system. Yet further, the present invention relates to a spark plug for use in such an ignition system for use in such an assembly.
An ignition system of this general type is disclosed in Swiss CH-PS 29 121. Such ignition system makes it possible to achieve multiple ignition with a single ignition coil and single interruptor or distributor, thus achieving a cost savings.
In the construction of airplane engines it has been the practice for some time to employ two conventional spark plugs and two ignition systems for safety reasons. For high quality passenger automotive vehicles, dual ignition with two spark plugs per cylinder and two ignition coils with related accessories also are known. Such arrangements however are expensive. Additionally, the use of conventional spark plugs in such dual ignition systems results in a disadvantage that the spark plugs are subjected to different thermal stresses with different engines and with different operating conditions or methods of driving.
The use of multiple ignition systems for internal combustion engines, particularly for engines of automotive vehicles, recently has been examined with renewed interest since such systems achieve a reduction in pollution due to better combustion of fuel.